KR20180135806A - Photomask blank, and preparation method thereof - Google Patents

Abstract

The present invention relates to a photomask blank for manufacturing a penetrating photomask for photolithography, which uses an exposure light with a wavelength of 200 nm or less to form a pattern on an object to be transferred. According to the present invention, the photomask blank comprises: a transparent substrate; a first film formed on the transparent substrate and made of a material etched by chlorine-oxygen based dry etching and resistant to a fluorine-based dry etching; and a second film formed to be in contact with the first film, made of a material including silica, and made of a material not substantially etched by chlorine-oxygen based dry etching. The second film comprises a single layer or multiple layers including at least one layer having a refractive index n of 1.6 or more, wherein the refractive index n is an optical parameter with respect to an inspection light of a greater wavelength than that of the exposure light used in a defect inspection process, or having an extinction coefficient k of 0.3 or more. Accordingly, a penetrating pinhole defect is able to be completely detected from a hard mask film made of a material including silica on an optical functional film.

Description

PHOTOMASK BLANK AND AND PREPARATION METHOD THEREOF FIELD OF THE INVENTION [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask blank which is a material of a photomask used for micro-fabrication of a semiconductor integrated circuit and the like, and a method of manufacturing the same.

2. Description of the Related Art In the field of semiconductor technology, research and development are being carried out to further miniaturize patterns. Particularly, in recent years, miniaturization of circuit patterns, thinning of wiring patterns, miniaturization of contact hole patterns for interlayer wiring constituting cells, and the like have progressed with the high integration of large-scale integrated circuits, The demand is getting higher and higher. Accordingly, in the field of photomask manufacturing technology used in the photolithography process at the time of micromachining, development of a technique for forming finer and more accurate circuit patterns (mask patterns) is required.

Generally, when a pattern is formed on a semiconductor substrate by a photolithography technique, reduction projection is performed. Therefore, the size of the pattern formed on the photomask is usually about four times the size of the pattern formed on the semiconductor substrate. In today's photolithographic technology, the size of the circuit pattern to be imaged is considerably lower than the wavelength of light used in exposure. Therefore, when the photomask pattern is formed by simply multiplying the size of the circuit pattern by a factor of four, the result that the original shape is not transferred to the resist film on the semiconductor substrate due to the influence of light, etc., .

Thus, by making the pattern formed on the photomask more complicated than the actual circuit pattern, the influence of the light interference or the like described above may be alleviated. As such a pattern shape, for example, there is a shape obtained by performing optical proximity correction (OPC) on an actual circuit pattern. In addition, techniques such as a modified illumination, a liquid immersion technique, and a double exposure (double patterning lithography) have been applied in order to follow the miniaturization and high precision of the pattern.

In forming the photomask pattern, for example, a photoresist film is formed on a photomask blank having a light-shielding film on a transparent substrate, a pattern is drawn by an electron beam, a resist pattern is obtained through development, Is used as an etching mask, the light shielding film is etched to form a light shielding pattern. However, in the case where the light shielding pattern is made finer and the film thickness of the resist film is kept the same as before the refinement, the ratio of the film thickness to the pattern, the so-called aspect ratio, becomes large and the pattern shape of the resist deteriorates, Or in some cases, the resist pattern is caused to collapse or exfoliate. Therefore, it is necessary to make the thickness of the resist film thin with the miniaturization.

Further, in order to reduce the load on a resist during dry etching, a method of using a hard mask has been tried before, for example, Japanese Patent Publication No. 63-85553 small (Patent Document 1) In, MoSi ₂ phase It has been reported that an SiO ₂ film is formed on an SiO ₂ film and this is used as an etching mask for MoSi ₂ dry etching using a gas containing chlorine and that the SiO ₂ film can also function as an antireflection film . Further, the use of chromium as the light shielding film on the phase shift film and the use of the SiO ₂ film as a hard mask thereon is described in, for example, Japanese Patent Application Laid-Open No. 7-49558 (Patent Document 2).

Japanese Patent Application Laid-Open No. 63-85553 Japanese Patent Application Laid-Open No. 7-49558

In the case of manufacturing a photomask using a photomask blank having a hard mask film, a mask pattern is first formed on the hard mask film, a mask pattern of the hard mask film is used as an etching mask, and a light- The mask pattern formed on the hard mask film is transferred. Therefore, if there is a penetration type pinhole defect penetrating the hard mask film in the thickness direction of the hard mask film, the penetration type pinhole defect is transferred directly to the optical function film and becomes a defect of the mask pattern of the optical function film In the defect inspection of the hard mask film, the detection of the through-hole type pinhole defect becomes very important.

On the other hand, from the viewpoint of miniaturization of the pattern, it is preferable that the hard mask film is thinner, but the thinner the film thickness, the more difficult it becomes to detect the penetrating pinhole defect. From the viewpoint of occurrence of defects at the time of development of a resist film (resist pattern) formed on the hard mask film, a SiO ₂ film is preferable as the hard mask film, but a material such as SiO ₂ has a refractive index n Or the extinction coefficient k is low, and in the case of these materials, it is further difficult to detect the penetrating pinhole defects.

A photomask blank having a hard mask film formed of a material containing silicon in contact with an optical functional film, which is provided to solve the above-described problems, is a hard mask capable of more reliably detecting a penetrating pinhole defect, A photomask blank having a film and a method of manufacturing the same are provided.

Means for Solving the Problems As a result of intensive investigations to solve the above problems, the present inventors have found that a fluorine-based dry etching process is performed by etching a chlorine-oxygen-based dry etching process using a transparent substrate and a mixed gas of chlorine gas and oxygen gas, And a second film composed of a material which is in contact with the first film and is made of a material containing silicon and which is substantially etched by chlorine oxygen based dry etching which etches the first film, Wherein the second film includes at least one layer having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more which is an optical constant with respect to an inspection light wavelength of a longer wavelength than the exposure light used in the defect inspection step By using a single layer or a multilayer structure, it is possible to provide a photolithography process in which a pattern is formed on a transfer object using exposure light having a wavelength of 200 nm or less A photomask blank used in the manufacture of a transmissive photomask to be used is a photomask blank having a film such as a hard mask film formed of a material containing silicon in contact with a film such as an optical functional film, The present invention has been accomplished on the basis of these findings.

Accordingly, the present invention provides the following photomask blank and a method of manufacturing the same.

Claim 1:

1. A photomask blank for producing a transmission type photomask for use in photolithography in which a pattern is formed on a transfer object by using exposure light having a wavelength of 200 nm or less,

A transparent substrate,

A first film formed on the transparent substrate and composed of a material which is etched by chlorine oxygen based dry etching using a mixed gas of chlorine gas and oxygen gas and which is resistant to fluorine dry etching by a fluorine containing gas,

A second film formed in contact with the first film and made of a material containing silicon and made of a material substantially etched by the chlorine oxygen based dry etching for etching the first film,

The second film is composed of a single layer or a multilayer including at least one layer having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more, which is an optical constant with respect to an inspection light wavelength of a long wavelength longer than the exposure light used in the defect inspection process Wherein the photomask blank is a photomask blank.

Claim 2:

The photomask blank according to claim 1, wherein the film thickness of the second film is 2 nm or more and 20 nm or less.

[Claim 3]

Wherein the material containing silicon in the second film is selected from the group consisting of silicon alone, silicon and a silicon-containing compound containing one or two or more light elements selected from oxygen, nitrogen and carbon, A photomask blank according to claim 1 or 2, comprising a transition metal silicon-containing compound containing one or more light elements and 20 atom% or less of transition metal.

Claim 4:

The photomask blank according to claim 3, wherein the light element includes one or both of oxygen and nitrogen.

[Claim 5]

The difference between the refractive index n of the layer having the highest refractive index n and the refractive index n of the layer having the highest refractive index n with respect to the wavelength of the inspection light is 0.5 or more or the layer having the highest extinction coefficient k for the inspection light wavelength is the lowest Wherein the difference in extinction coefficient k of the layer is not less than 0.3.

[Claim 6]

The total content of oxygen and nitrogen in the layer which is the farthest from the first film in the second film is higher than the total content of oxygen and nitrogen in the layer in contact with the first film. A photomask blank as described.

Claim 7

The photomask blank according to any one of claims 1 to 6, wherein the defect is a through-hole pinhole defect.

Claim 8:

The photomask blank according to any one of claims 1 to 7, wherein the exposure light is an ArF excimer laser.

Claim 9:

The photomask blank according to claim 8, wherein the inspection light wavelength is one wavelength selected from a wavelength of 600 nm or less.

Claim 10:

A method of manufacturing a photomask blank according to any one of claims 1 to 9, comprising the step of inspecting a defect at the inspection light wavelength.

According to the photomask blank of the present invention, penetrating pinhole defects of a hard mask film formed of a material containing silicon on an optical functional film can be reliably detected.

1 is a cross-sectional view showing an example of a photomask blank of the present invention.
2 is a cross-sectional view showing another example of the photomask blank of the present invention.

Hereinafter, the present invention will be described in more detail.

A photomask blank of the present invention is a photomask blank for producing a transmissive photomask for use in photolithography in which a pattern is formed on a transfer object using exposure light having a wavelength of 200 nm or less (light used in exposure using a photomask) It is a blank. In the photomask blank and the photomask of the present invention, the exposure light is preferably ArF excimer laser light (wavelength: 193 nm).

The photomask blank of the present invention has a transparent substrate, a first film formed on the transparent substrate, and a second film formed in contact with the first film. Specifically, a photomask blank in which a first film 21 and a second film 22 are formed in this order on a transparent substrate 1 as shown in Fig. 1 can be mentioned.

As the transparent substrate, there is no particular limitation on the type of the substrate and the substrate size, but a transparent quartz substrate or the like is applied at a wavelength used as an exposure wavelength. For example, a transparent substrate having a size of 6 inches (square) Lt; RTI ID = 0.0 > 6025 < / RTI > When a SI unit system is used, the 6025 substrate is usually referred to as a transparent substrate having a 152 mm square and a thickness of 6.35 mm.

The first film may be formed in contact with the transparent substrate (directly on the transparent substrate), or may be formed with another film (for example, a phase shift film or the like) between the transparent substrate and the transparent substrate. Specifically, as shown in Fig. 2, a photomask blank (third film) 3 in which another film (third film) 3, a first film 21 and a second film 22 are sequentially formed on a transparent substrate 1 . The other film is a material which is etched by fluorine dry etching with a material having a different etching property from that of the first film, particularly a fluorine-containing gas, and is resistant to chlorine oxygen system dry etching by a mixed gas of chlorine gas and oxygen gas, It is preferable that it is made of a material containing silicon. The other film may be composed of a single layer or may be composed of multiple layers.

The first film is composed of a material which is etched by chlorine oxygen based dry etching by a mixed gas of chlorine gas and oxygen gas and is resistant to fluorine dry etching by a gas containing fluorine. Specific examples of such materials include chromium oxide, chromium oxide (CrO), chromium nitride (CrN), chromium carbide (CrC), chromium oxide nitride (CrON), chromium oxycarbide (CrOC), chromium nitride carbide Chromium compounds such as image quality carbide (CrONC) and the like.

When the first film is a film formed of a chromium compound, the content of chromium is preferably 30 atomic% or more, particularly 40 atomic% or more, more preferably 100 atomic% or less, particularly 90 atomic% or less. The content of oxygen is 0 atomic% or more, especially 1 atomic% or more, 60 atomic% or less, particularly 40 atomic% or less, the content of nitrogen is 0 atomic% or more, particularly 1 atomic% or more and 50 atomic% , Particularly not more than 40 atomic%, carbon content of not less than 0 atomic%, particularly preferably not less than 1 atomic% and not more than 20 atomic%, more preferably not more than 10 atomic%, when it is necessary to adjust the etching rate. In this case, the total content of chromium, oxygen, nitrogen and carbon is preferably 95 atomic% or more, particularly preferably 99 atomic% or more, particularly preferably 100 atomic%.

The first film may be composed of a single layer or a multilayer structure. In the case of a single layer, it may be a single composition layer whose composition is constant in the thickness direction, or a composition gradient layer whose composition continuously changes in the thickness direction. On the other hand, in the case of a multi-layer structure, it is composed of two or more layers selected from a single composition layer whose composition is constant in the thickness direction and a composition gradient layer whose composition continuously changes in the thickness direction, A combination of a single composition layer and a composition gradient layer may be used. In the composition gradient layer, the constituent elements may be increased or decreased along the thickness direction.

It is preferable that the film thickness (total film thickness) of the first film is 20 nm or more, particularly 40 nm or more, and 100 nm or less, particularly 70 nm or less. The first film is preferably a film formed as an optically functional film such as a light-shielding film or an antireflection film. The first film may also function as a hard mask (etching mask) for etching the above-mentioned other film formed on the transparent substrate side or the transparent substrate.

The second film is composed of a material which is made of a material containing silicon and which is substantially etched by chlorine oxygen based dry etching for etching the first film, that is, chlorine oxygen based dry etching by a mixed gas of chlorine gas and oxygen gas . The second film is preferably a material which is etched by fluorine dry etching with a fluorine-containing gas.

In the film that functions as an etching mask for a film existing on the transparent substrate side such as a hard mask film, it is important to detect the through-hole type pinhole, and defect detection in the manufacturing process of the photomask blank is performed by exposure light The wavelength of the inspection light of a longer wavelength is generally used. When the exposure light is an ArF excimer laser, the wavelength of the inspection light is generally one wavelength selected from a wavelength of 600 nm or less, for example, 213 nm, 355 nm, 488 nm and 532 nm. M6640 (inspection wavelength: 532 nm) and M8350 (inspection wavelength: 355 nm) manufactured by Laser Tech Co., Ltd. are used as a defect detection apparatus that uses such a wavelength as an inspection light wavelength. Further, in the future, it is considered that the inspection light wavelength of the defect inspection shifts to the shorter wavelength side in order to improve the detection sensitivity of the micro defect as the monochromatic photomask pattern is miniaturized.

In the defect detection of the photomask blank, particularly the detection of the through-hole type pinhole defect, the refractive index n and the extinction coefficient k, which are the optical constants of the film, influence the detection sensitivity of the micro-defect. In the photomask blank of the present invention, it is preferable that the second film is a single layer or multiple layers including at least one layer having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more with respect to an inspection light wavelength of a longer wavelength than the exposure light used in the defect inspection step . It is preferable that the refractive index n and the extinction coefficient k are high. From the viewpoint of defect detection, furthermore, it is preferable that the refractive index n is 1.7 or more and the extinction coefficient k is 0.5 or more. The refractive index n is generally 7 or less, and the extinction coefficient k is generally 6 or less.

As the material containing silicon constituting the second film, a silicon group can be exemplified. The silicon group is the most effective material from the viewpoint of defect detection because the refractive index n and the extinction coefficient k are high. As the material containing silicon constituting the second film, a silicon-containing compound, for example, a silicon-containing compound containing silicon and at least one light element selected from oxygen, nitrogen and carbon, specifically silicon oxide (SiO2), silicon nitride (SiN), silicon carbide (SiC), silicon oxynitride (SiON), silicon oxycarbide (SiOC), silicon nitride carbide (SiNC), silicon oxynitride carbide (SiONC) (Me), a transition metal silicon oxide (MeSiO), a transition metal silicon nitride (MeSiN), a transition metal compound containing one or more elements selected from oxygen, nitrogen and carbon and a transition metal silicon- Metal silicon carbide (MeSiC), transition metal silicon oxynitride (MeSiON), transition metal silicon oxycarbide (MeSiOC), transition metal silicon nitride carbide (MeSiNC), transition metal silicon oxynitride carbide (MeSiONC) and the like. Examples of the transition metal (Me) include titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum ) And tungsten (W) are preferable.

When the material containing silicon in the second film is a silicon-containing compound, the content of silicon is preferably 20 atomic% or more, particularly 33 atomic% or more, and preferably 95 atomic% or less, particularly preferably 80 atomic% or less. When the etching rate needs to be adjusted, the oxygen content is preferably 1 atomic% or more, more preferably 20 atomic% or more, and 70 atomic% or less, particularly preferably 66 atomic% or less, The content of carbon is 0 atomic% or more, particularly 1 atomic% or more, and 20 atomic% or less, particularly 10 atomic% or more, more preferably 1 atomic% or more, Or less. In this case, the total content of silicon, oxygen, nitrogen, and carbon is preferably 95 atomic% or more, particularly preferably 99 atomic% or more, particularly preferably 100 atomic%.

On the other hand, when the material containing silicon in the second film is a transition metal silicon-containing compound, the content of silicon is preferably 20 atomic% or more, particularly 33 atomic% or more, and 90 atomic% or less, particularly preferably 80 atomic% or less. When the etching rate needs to be adjusted, the oxygen content is preferably 1 atomic% or more, more preferably 20 atomic% or more, and 70 atomic% or less, particularly preferably 66 atomic% or less, The content of carbon is 0 atomic% or more, particularly 1 atomic% or more, and 20 atomic% or less, particularly 10 atomic% or more, more preferably 1 atomic% or more, Or less. The content of the transition metal is 20 atomic% or less, but preferably 15 atomic% or less, particularly 10 atomic% or less. In this case, the total content of silicon, oxygen, nitrogen, carbon and transition metal is preferably 95 atomic% or more, particularly preferably 99 atomic% or more, especially 100 atomic%.

The silicon-containing compound and the transition metal silicon-containing compound constituting the second film preferably contain one or both of oxygen and nitrogen, particularly oxygen, as the light element.

The second film may be composed of a single layer or may be composed of multiple layers (for example, two to four layers). In the case of a single layer, it may be a single composition layer whose composition is constant in the thickness direction, or a composition gradient layer whose composition continuously changes in the thickness direction. On the other hand, in the case of a multi-layer structure, it is composed of two or more layers selected from a single composition layer whose composition is constant in the thickness direction and a composition gradient layer whose composition continuously changes in the thickness direction, A combination of a single composition layer and a composition gradient layer may be used. In the composition gradient layer, the constituent elements may be increased or decreased along the thickness direction. The composition gradient layer can be configured so that the refractive index n or the extinction coefficient k increases or decreases along the thickness direction. From the viewpoint of detection of the penetrating pinhole defect, it is preferable that all the second film and the compositionally graded layer constituting the second film are all directed in a direction away from the transparent substrate so that the refractive index n or the extinction coefficient k decreases desirable.

The second film may be a single layer from the viewpoint of the etching rate of the film at the time of processing and the occurrence of defects at the time of film formation but it is preferable that the second film has a multilayer structure including one or more layers having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more desirable. However, when the refractive index n and the extinction coefficient k are set to be equal to or larger than the predetermined value or the refractive index n and the extinction coefficient k are equal to or larger than the predetermined value, By combining layers that do not satisfy these ranges, electrons can be used as a layer contributing to improvement of defect inspection accuracy, the latter being a favorable layer for functions other than the improvement of defect inspection accuracy, , A film having a better function can be obtained.

For example, from the viewpoint of adhesion with a photoresist and development defects, the outermost surface portion (the side most distant from the transparent substrate) of the second film is preferably silicon dioxide (SiO ₂ ), for example, Since the refractive index n and the extinction coefficient k are low in the light wavelength, it is effective to form the second film into a multilayer including one or more layers having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more.

When the second film is a multilayer, it is preferable that the ratio of the layer having a refractive index n of 1.6 or more or the extinction coefficient k of 0.3 or more to the film thickness of the entire second film is 20% or more, particularly 30% or more . From the viewpoint of sufficiently obtaining the functions other than the improvement of the accuracy of the defect inspection, the layer which does not satisfy the range of the refractive index n of 1.6 or more or the extinction coefficient k of 0.3 or more is set to 40% Or more, particularly preferably 50% or more.

When the second film is made of a multilayer, the difference between the refractive index n of the layer with the highest refractive index n and the refractive index n with respect to the wavelength of the inspection light is preferably 0.5 or more, particularly 0.7 or more, it is preferable that the difference between the extinction coefficient k of the layer having the highest value of k and the extinction coefficient k of the lowest layer is 0.3 or more, particularly 0.5 or more. The layer having the highest refractive index n and the layer having the highest refractive index n and the layer having the lowest extinction coefficient k for the lowest wavelength or the wavelength of the inspection light may be disposed at any position of the second film. For example, in the case of a two-layer structure, one of the layer having the highest refractive index n and the layer having the highest extinction coefficient k for the lowest wavelength or the wavelength of the inspection light is disposed on the transparent substrate side, As shown in Fig. When the second film is composed of three or more layers, either the layer having the highest refractive index n and the layer having the lowest extinction coefficient k or the lowest layer having the lowest extinction coefficient k for the inspection light wavelength are disposed on the transparent substrate side, And the other is disposed on the side away from the transparent substrate, particularly on the side farthest from the transparent substrate.

In the silicon-containing compound and the transition metal silicon-containing compound constituting the second film, it is particularly preferable to include one or both of oxygen and nitrogen, particularly oxygen, as the light element, , It is preferable that the total content of oxygen and nitrogen in the layer on the side farthest from the first film is higher than the total content of oxygen and nitrogen in the layer in contact with the first film.

The thickness of the second film is sufficient to prevent the first film from being lost in etching, but it is preferable that the second film is not so thick from the viewpoint of pattern formation. Therefore, it is preferable that the film thickness (total film thickness) of the second film is 2 nm or more, particularly 5 nm or more, and 20 nm or less, particularly 10 nm or less. The second film is preferably a film formed as a hard mask film (etching mask film). The second film may be a film that is completely removed when the photomask is used, and may be a film that plays a part of the functions of a light-shielding film, an antireflection film, or the like. The film may be a photomask, Film.

When the first film is formed with another film (third film) interposed between the first film and the transparent substrate, a silicon-containing compound such as silicon and oxygen and nitrogen (Si), silicon oxynitride (SiON), or the like, or a transition metal silicon compound such as a transition metal (Me) and a silicon compound containing at least one element selected from the group consisting of silicon A transition metal silicon oxide (MeSiO), a transition metal silicon nitride (MeSiN), a transition metal silicon carbide (MeSiC), a transition metal silicon carbide (MeSiC), and a transition metal silicon compound containing at least one element selected from oxygen, Transition metal silicon oxynitride (MeSiON), transition metal silicon oxycarbide (MeSiOC), transition metal silicon nitride carbide (MeSiNC), and transition metal silicon oxynitride carbide (MeSiONC). Examples of the transition metal (Me) include titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum ) And tungsten (W), but molybdenum (Mo) is particularly preferable from the viewpoint of dry etching workability.

When the other film is a phase shift film, the phase shift film may be a completely transmissive phase shift film or a halftone phase shift film (for example, a transmittance to exposure light of 5 to 30%). The film thickness of the phase shift film is a film thickness which shifts the phase to a predetermined amount, usually 150 ° or more, particularly 170 ° or more, and 200 ° or less, particularly 190 ° or less with respect to the exposure light when using the photomask, As shown in FIG. Specifically, for example, it is preferably 50 nm or more, particularly 55 nm or more, and 80 nm or less, particularly preferably 75 nm or less.

When the light shielding film or the light shielding film and the antireflection film are formed as the first film directly on the transparent substrate of the present invention, the photomask blank of the present invention is formed by using a phase shift film When one film is formed, a phase shift type photomask blank can be obtained. A phase shift type photomask (phase shift mask) can be manufactured from a binary type photomask blank (binary mask) and a phase shift type photomask blank from a binary type photomask blank.

It is preferable that each single layer and multilayer of the first film, the second film and the other film of the present invention is formed by a sputtering method in which a film excellent in homogeneity can be easily obtained and any of DC sputtering and RF sputtering can be used . The target and the sputter gas are appropriately selected according to the refractive index n or the extinction coefficient k to be set, and further, the layer composition, the composition, and the like. The content ratio of the rare earth element can be adjusted by using a reactive gas for the sputter gas and a reactive sputtering by appropriately adjusting the amount of the introduced gas. Specific examples of the reactive gas include an oxygen-containing gas, a nitrogen-containing gas, a carbon-containing gas and the like, specifically oxygen gas (O ₂ gas), nitrogen gas (N ₂ gas), nitrogen oxide gas (NO gas, N ₂ O gas, NO ₂ Gas), carbon oxide gas (CO gas, CO ₂ gas), or the like can be used. As the sputter gas, an inert gas such as helium gas, neon gas or argon gas may be used as the rare gas, and an inert gas is preferably argon gas. The sputter pressure is usually 0.01 Pa or more, particularly 0.03 Pa or more, and 10 Pa or less, particularly 0.1 Pa or less.

When the films are constituted of multiple layers, the respective layers may be formed in different sputter chambers or may be formed while changing the sputtering conditions stepwise or continuously in the same sputter chamber, but from the viewpoint of productivity, it is better to form the films in the same chamber. In this case, it is preferable to form the film so that the number of light elements increases as the film formation progresses due to the film forming property by the sputtering method. In this case, the refractive index n or the extinction coefficient k From the transparent substrate to the side closest to the transparent substrate and the side with the lowest index of refraction n or the minimum extinction coefficient k on the side farthest from the transparent substrate.

The film composed of a material containing chromium may be formed as a target by using a chromium target, a target added with one or more optional elements selected from oxygen, nitrogen and carbon, or the like, depending on the composition of the film to be formed . Further, the film composed of a material containing silicon can be formed as a target using a target selected from a silicon target, a transition metal target, a transition metal silicon target, or the like, depending on the composition of the film to be formed.

The photomask blank of the present invention includes a step of inspecting a defect in a photomask blank, particularly a penetrating pinhole defect, at an inspection light wavelength of a longer wavelength than that of an exposure light when the photomask blank is manufactured by the above- , Defects of the photomask blank, particularly the through-hole pinholes, are detected with good sensitivity.

[Example]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1, Comparative Example 1]

A 6025 quartz substrate of 152 mm square and 6.35 mm in thickness was provided in a chamber of a sputtering apparatus. A 60 nm quartz substrate of SiN having a film thickness of 60 nm (made of SiN) was formed in contact with the transparent substrate by using a Si target, argon gas and nitrogen gas Film) was formed. Subsequently, using a Cr target and argon gas, a light-shielding film (first film) of Cr having a film thickness of 54 nm was formed in contact with the phase shift film. Subsequently, a single-layered hard mask film (second film) made of a material containing silicon and having a thickness of 10 nm was formed using a Si target and argon gas and, if necessary, oxygen gas or nitrogen gas.

The hard mask film is formed by appropriately setting the introduction amount (flow rate) of the oxygen gas or the nitrogen gas and setting the hard mask film to five kinds of different compositions from the layer made of a single silicon layer, the layer made of silicon oxide (SiO 2), and the layer made of silicon nitride Samples 1 to 5 were prepared. The composition of the obtained hard mask film was measured by an X-ray photoelectron spectroscopy (XPS) apparatus (K-Alpha manufactured by Thermo Scientific Co., Ltd.). The refractive index n and the extinction coefficient k, which are optical constants of the respective wavelengths of these hard mask films, were measured with a spectroscopic ellipsometer (VUV-VASE Gen-II manufactured by J. A. Woollam Co., Inc.). The results are shown in Tables 1 and 2.

Subsequently, for each 120 nm? Penetration type pinhole defect in the hard mask film of Samples 1 to 5, the contrast at the inspection light wavelength of 532 nm was simulated based on the refractive index n and the extinction coefficient k measured in Samples 1 to 5 To evaluate the detection sensitivity of defects. The results are shown in Table 3.

[Example 2, Comparative Example 2]

A 6025 quartz substrate of 152 mm square and 6.35 mm in thickness was provided in a chamber of a sputtering apparatus. A 60 nm quartz substrate of SiN having a film thickness of 60 nm (made of SiN) was formed in contact with the transparent substrate by using a Si target, argon gas and nitrogen gas Film) was formed. Subsequently, using a Cr target and argon gas, a light-shielding film (first film) of Cr having a film thickness of 54 nm was formed in contact with the phase shift film. Subsequently, a hard mask film (second film) having a two-layer structure or a single layer made of a material containing silicon was formed using a Si target and argon gas and, if necessary, an oxygen gas or a nitrogen gas.

The hard mask film was obtained by setting the introduction amount (flow rate) of the oxygen gas or the nitrogen gas appropriately and setting the amount of the silicon oxide (SiO 2) and the silicon nitride (SiN) Samples 6 to 14 were prepared under five different conditions of the same composition as in Examples 1 to 6. In Samples 6 to 13, (1) a layer thickness of 8 nm on the surface side (the side away from the transparent substrate), a layer thickness of 2 nm on the transparent substrate side (10 nm of the entire hard mask film) (3) a layer thickness of 5 nm on the surface side, and a layer thickness of 5 nm on the transparent substrate side (a thickness of the entire hard mask film: 10 nm) Layer hard mask film, and in the sample 14, a single-layered hard mask film having a total thickness of 10 nm or 5 nm was formed as the entire hard mask film. The layer composition (composition) of each sample is shown in Table 4.

Subsequently, the contrast at the inspection light wavelength of 532 nm was measured for the through-hole type pinhole defects of 120 nm in each of the hard mask films of Samples 6 to 14, and the contrast at the inspection light wavelength of 532 nm was measured using the refractive index n And the extinction coefficient k, and the detection sensitivity of the defect was evaluated. The results are shown in Table 5.

1: transparent substrate
21: First film
22: The second film
3: another film (third film)

Claims (10)

1. A photomask blank for producing a transmission type photomask for use in photolithography in which a pattern is formed on a transfer object by using exposure light having a wavelength of 200 nm or less,
A transparent substrate,
A first film formed on the transparent substrate and composed of a material which is etched by chlorine oxygen based dry etching using a mixed gas of chlorine gas and oxygen gas and which is resistant to fluorine dry etching by a fluorine containing gas,
A second film formed in contact with the first film and made of a material containing silicon and made of a material substantially etched by the chlorine oxygen based dry etching for etching the first film,
The second film is composed of a single layer or a multilayer including at least one layer having a refractive index n of 1.6 or more or an extinction coefficient k of 0.3 or more, which is an optical constant with respect to an inspection light wavelength of a long wavelength longer than the exposure light used in the defect inspection process Wherein the photomask blank is a photomask blank. The photomask blank according to claim 1, wherein the film thickness of the second film is 2 nm or more and 20 nm or less. The method according to claim 1 or 2, wherein the material containing silicon in the second film is at least one selected from the group consisting of silicon, silicon, and silicon-containing compounds containing one or two or more light elements selected from oxygen, nitrogen and carbon, And a transition metal silicon-containing compound containing one or two or more light elements selected from oxygen, nitrogen and carbon and 20 atom% or less of transition metal. The photomask blank according to claim 3, wherein the light element includes one or both of oxygen and nitrogen. The optical fiber according to claim 1 or 2, wherein the second film has a multilayer structure, and the difference between the refractive index n of the layer having the highest refractive index n and the refractive index n of the lowest layer with respect to the inspection light wavelength is 0.5 or more, Wherein the difference between the extinction coefficient k of the layer having the highest extinction coefficient k and the extinction coefficient k of the lowest layer is 0.3 or more. The method according to claim 5, wherein the total content of oxygen and nitrogen in the layer farthest from the first film in the second film is higher than the total content of oxygen and nitrogen in the layer in contact with the first film Characterized by a photomask blank. The photomask blank according to claim 1 or 2, wherein the defect is a penetrating pinhole defect. The photomask blank according to claim 1 or 2, wherein the exposure light is an ArF excimer laser. The photomask blank according to claim 8, wherein the inspection light wavelength is one wavelength selected from a wavelength of 600 nm or less. A method of manufacturing a photomask blank according to any one of claims 1 to 3, comprising the step of inspecting a defect at the inspection light wavelength.

Images